Changes in equivalent and gradient refractive index of the crystalline lens with accommodation
Changes in equivalent and gradient refractive index of the crystalline lens with accommodation
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DOI：
10.1097/00006324-199702000-00024
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发表时间：
1997-02-01
影响因子：
1.4
通讯作者：
Smith, G
中科院分区：
文献类型：
--
作者：
Garner, LF;Smith, G
采用角膜曲率计、自动验光、A型超声检查和视频角膜屈光度测量技术，对11名年龄在18 - 28岁（平均21.2 ± 2.62岁）的受试者在0.0、1.5、3.5、5.5和8.0 D的调节刺激水平下的眼球尺寸和屈光进行测量。受试者的屈光不正范围为+0.50至-4.25 D，平均-1.88 +/- 1.64 D。在最大调节水平下，前房深度减少了0.23 +/- 0.09 mm，透镜厚度增加了0.28 +/- 0.09 mm，眼轴长度或玻璃体腔深度没有记录到显著差异。晶体透镜前表面的曲率半径从11.54 +/- 1.27 mm降至6.59 +/- 0.97 mm，后表面从-6.67 +/- 0.97 mm降至-5.30 +/- 0.4 mm。我们确定等效折射率为1.4277 +/- 0.0011，在不同的适应水平上没有显著差异。当晶体透镜被建模为具有椭圆等折射率线的梯度折射率（GRIN）结构时，对于1.406的假定中心折射率，透镜的平均表面折射率为1.3859 +/-0.0009。透镜前表面的屈光度从4.38 +/- 0.49增加到7.59 +/- 0.34 D，后表面从7.67 +/- 1.28增加到9.32 +/- 0.64 D，最大反射刺激8.00D时，GRIN功率由9.70 ± 1.31增加到13.74 ± 0.77D。基于所使用的模型，调节性晶状体透镜的屈光力增加的很大一部分是由于透镜内折射率分布的变化。
The ocular dimensions and refraction of the eye were measured for accommodation stimulus levels of 0.0, 1.5, 3.5, 5.5, and 8.0 D for 11 subjects aged 18 to 28 years, mean 21.2 +/- 2.62 years using keratometry, autorefraction, A-Scan ultrasonography, and video phakometry techniques. The subjects had refractive errors in the range +0.50 to -4.25 D, mean -1.88 +/- 1.64 D. With the maximum level of accommodation the anterior chamber depth decreased by 0.23 +/- 0.09 mm, the lens thickness increased by 0.28 +/- 0.09 mm, and no significant differences were recorded in axial length or vitreous chamber depth. The radius of curvature of the anterior surface of the crystalline lens decreased from 11.54 +/- 1.27 to 6.59 +/- 0.97 mm and the posterior surface from -6.67 +/- 0.97 to -5.30 +/- 0.4 mm. We determined the equivalent refractive index to be 1.4277 +/- 0.0011, with no significant differences at different levels of accommodation. When the crystalline lens was modeled as a gradient refractive index (GRIN) structure with elliptical iso-indicial lines, the mean surface refractive index of the lens was 1.3859 +/- 0.0009 for an assumed central refractive index of 1.406. The power of the anterior surface of the lens increased from 4.38 +/- 0.49 to 7.59 +/- 0.34 D, the posterior surface increased from 7.67 +/- 1.28 to 9.32 +/- 0.64 D, and the GRIN power increased from 9.70 +/- 1.31 to 13.74 +/- 0.77 D for the maximum accommodative stimulus of 8.00 D. On the basis of the model used, a substantial part of the increase in power of the crystalline lens with accommodation resulted from the change in refractive index: distribution within the lens.